There is obviously no official statistic but I believe in many cases when casinos ask for KYC it is because their terms and conditions allow them the flexibility to do it regardless of whether legitimate reasons exist or not. I cannot state what is going on in your particular case but surely you have to accept you willingly signed up to their terms of service when you registered on their platform therefore they effectively hold all the power.
What that means is whether or not any rules were broken (or deemed to have been broken) they have the absolute authority to do what they want and that is not limited to Shuffle, virtually all casinos operate under similar terms and conditions.
I have made it very clear from years ago there is a risk when sending KYC to online casinos and gaming websites because most are anonymous and can sell your private data including documents on the black market. If you are giving up on them after sending your ID and now consider your funds lost, why did you do it in the first place when you always suspected their end game?
In the chat screenshots you made very bold claims about your account on Stake therefore if you had a bad experience at Shuffle I would advise you to get past the setback and forget abut Shuffle and instead focus on Stake.
I went ahead and submitted my ID and now they further verification for KYC3! like utility or bank statement . Which is not even available for my country (according to settings) they want me to provide it in live chat.
As I predicted and probably after providing that they will ask me to take selfie or video calll just to further hassle me. I won't entertain them anymore and consider my deposit/money gone. But be careful with this shady casino
